Scarifiers are working machines used for working and removing soils, in particular for making roads. In their standard constructional form these machines are provided with a milling drum having a plurality of active elements, e.g. cutting or milling elements, that—during rotation of the milling drum—come into contact with the surface to be removed and crush it.
In some prior art scarifiers, each active element is a tool arrangement consisting of a support base fixed to the tubular body of the milling drum, wherein the support base accomodates a respective toolholder in which a milling tool is removably inserted, for example, by pressing it into the toolholder.
The active elements are arranged on the milling drum corresponding to one or more right hand and left hand spirals starting from both ends of the milling drum and meeting at a central location on the milling drum. The required pitch of the spirals defined by the active elements varies according to the kind of soil to be worked on. Specifically, small pitches are adapted to work on hard asphalt and to carry out soil forming while large pitches are particularly adapted to carry out digging on concrete or soft mix.
For optimizing the working process, it is desired to have for each scarifier a couple of drums available, whereby these drums are provided with different pitches of the tools supported thereon so as to adapt the scarifier to the kind of soil to be worked on. In order to avoid the necessity of changing milling drums, it is known to provide a single milling drum with double threaded spirals having a small pitch, and thus adapted to work on hard asphalt or to carry out forming. Such a milling drum may be used also to carry out diggings on concrete or soft mix by removing the toolholders with the relevant tools arranged in the support bases along one of the adjacent spirals. Then, the same milling drum has the active elements arranged on a single spiral having a pitch which is about doubled to the previous one, so that it can efficiently be used for digging concrete or soft mix as well.
There are various support bases known in the art, which generally have to be of a solid construction to provide the required stability during operation of the milling drum. This constructions may be so volumnous that an empty support base interferes with a tool remaining on the milling drum. Also, in order to fixedly mount the toolholders to the respective support bases reliable connection means are required which often render the assembly and disassembly of the toolholders labour intensive.